Method for separating multi-phase mixtures of solvents having small differences in density

Abstract

The invention relates to an apparatus for separating water-containing solvent mixtures having two or more phases, using one or two gravitational separators ( 4, 16 ) and to the use of this apparatus, and also to a process for separating water-containing solvent mixtures having two or more phases. Using the novel apparatus it is possible to separate even small-density-difference solvent mixtures having two or more phases. To this end, a coalescence separator ( 1 ) has been provided upstream of the first gravitational separator ( 4 ).

What is claimed is:  
     
       1. A process for separating water-containing solvent mixtures having two or more phases comprising the steps 
       a) feeding the mixture to be separated to a coalescence separator ( 1 );  
       b) enlarging a volume of droplets of one component of the mixture in the coalescence separator ( 1 );  
       c) feeding the solvent mixture with enlarged droplet volume to a gravitational separator ( 4 );  
       d) separating the solvent mixture in the gravitational separator ( 4 ) into a first phase A ( 6 ), which is composed predominantly of solvent, into a second phase B ( 7 ), which comprises a mixture of water and solvent, and into a third phase C ( 8 ), which is composed predominantly of water, wherein the second phase B ( 7 ) is pumped from the gravitational separator ( 4 ) to the coalescence separator ( 1 ), and the pumping is controlled via a sensor ( 10 ), which detects the level of the second phase B ( 7 ) in the gravitational separator ( 4 ).  
     
     
       2. The process as claimed in  claim 1 , wherein the third phase C ( 8 ) is discharged from the gravitational separator ( 4 ) and the discharge is controlled via a sensor ( 21 ) detecting the level of the third phase C ( 8 ). 
     
     
       3. A process for separating water-containing solvent mixtures comprising 
       feeding a mixture of water and of an organic solvent to a coalescence separator;  
       passing the mixture in the coalescence separator through a filler material;  
       feeding the mixture to a gravitational separator through a feed line in such a way that the feed in point is below a liquid surface of the gravitational separator;  
       separating the mixture in the gravitational separator into an upper phase composed predominantly of organic solvent, into a middle phase composed of water and of organic solvent, and a lower phase predominantly composed of water, wherein the middle phase is pumped from the gravitational separator to the coalescence separator, and the pumping is controlled via a sensor, which detects the level of the middle phase in the gravitational separator.  
     
     
       4. The process for separating water-containing solvent mixtures according to  claim 3 , wherein the mixture fed to the coalescence separator comprises small water droplets dispersed in an organic solvent; and further comprising 
       employing the filler material composed of solvent resistant foam;  
       enlarging the water droplets in the filler material;  
       substantially separating the water from the organic solvent in the filler material.  
     
     
       5. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       regulating the feeding of the mixture into the gravitational separator with a control valve disposed in the feed line.  
     
     
       6. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       controlling the height of the middle phase in the gravitational separator with the sensor, wherein the sensor is arranged inside the gravitational separator.  
     
     
       7. The process for separating water-containing solvent mixtures according to  claim 6  further comprising 
       measuring the electrical conductivity of the middle phase with the aid of the sensor.  
     
     
       8. The process for separating water-containing solvent mixtures according to  claim 6  further comprising 
       measuring the opacity of the middle phase with the aid of the sensor.  
     
     
       9. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       feeding liquid from the middle phase into a circulation line and through a valve to an input of the coalescence separator;  
       delivering a signal from the sensor to the valve in case a level of the middle phase exceeds a certain maximum value.  
     
     
       10. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       feeding liquid from the middle phase into a circulation line and through a pump to an input of the coalescence separator;  
       delivering a signal from the sensor to the pump in case a level of the middle phase exceeds a certain maximum value.  
     
     
       11. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       removing the upper phase composed predominantly of organic solvent from the gravitational separator for reuse.  
     
     
       12. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       monitoring a height level of the lower phase predominantly composed of water with a second sensor by measuring electrical conductivity of the lower phase;  
       discharging the lower phase through a discharge line with an outlet valve connected to a base of the gravitational separator;  
       passing a control pulse from the second sensor to the outlet valve if a surface level of the lower phase rises above the level of the second sensor.  
     
     
       13. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       monitoring a height level of the lower phase predominantly composed of water with a second sensor by measuring opacity of the lower phase;  
       discharging the lower phase through a discharge line with an outlet valve connected to a base of the gravitational separator;  
       passing a control pulse from the second sensor to the outlet valve if a surface level of the lower phase rises above the level of the second sensor.  
     
     
       14. The process for separating water-containing solvent mixtures according to  claim 3  further comprising 
       furnishing the gravitational separator in a configuration of an upper tank disposed on top of a lower tank, wherein a top of the lower tank is connected to a bottom of the upper tank and wherein the middle phase is disposed in the area of a connection between the lower tank and the upper tank.  
     
     
       15. The process for separating water-containing solvent mixtures according to  claim 3 , wherein the mixture fed to the coalescence separator comprises small water droplets dispersed in an organic solvent; and further comprising 
       employing the filler material composed of solvent resistant foam;  
       enlarging the water droplets in the filler material;  
       substantially separating the water from the organic solvent in the filler material;  
       regulating the feeding of the mixture into the gravitational separator with a control valve disposed in the feed line;  
       controlling the height of the middle phase in the gravitational separator with the sensor, wherein the sensor is arranged inside the gravitational separator;  
       measuring the electrical conductivity of the middle phase with the aid of the sensor;  
       measuring the opacity of the middle phase with the aid of the sensor;  
       feeding liquid from the middle phase into a circulation line and through a valve to an input of the coalescence separator;  
       delivering a signal from the sensor to the valve or pump in case a level of the middle phase exceeds a certain maximum value;  
       removing the upper phase composed predominantly of organic solvent from the gravitational separator for reuse;  
       monitoring a height level of the lower phase predominantly composed of water with a second sensor by measuring electrical conductivity of the lower phase;  
       discharging the lower phase through a discharge line with an outlet valve connected to a base of the gravitational separator;  
       passing a control pulse from the second sensor to the outlet valve if a surface level of the lower phase rises above the level of the second sensor;  
       monitoring a height level of the lower phase predominantly composed of water with a second sensor by measuring opacity of the lower phase;  
       discharging the lower phase through a discharge line with an outlet valve connected to a base of the gravitational separator;  
       passing a control pulse from the second sensor to the outlet valve if a surface level of the lower phase rises above the level of the second sensor furnishing the gravitational separator in a configuration of an upper tank disposed on top of a lower tank, wherein a top of the lower tank is connected to a bottom of the upper tank and wherein the middle phase is disposed in the area of a connection between the lower tank and the upper tank.